Heater sling

ABSTRACT

The heater sling according to this invention is capable of lifting, moving and positioning a workpiece. In particular, it relates to a device and method for lifting a circumferential heater used in the manufacture of silicon ingots by the Czochralski method. The invention operates by mechanically extending a plurality of slings under a workpiece, lifting the workpiece, and placing it in a desired location.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and method for lifting,moving and positioning a workpiece. In particular, it relates to adevice and method for lifting a circumferential heater used in themanufacture of silicon ingots by the Czochralski method.

2. Description of the Prior Art

Traditionally, devices used to lift circumferential heaters used in themanufacture of silicon ingots are lowered around the outside edge of theheater. Slider bars are then inserted under the heater, and secured tothe lifter. In some instances, a cage is then placed around the heater.Prior devices required an operator to manually place support platesunder the heater, attach a cage to the supports, and then attach thisapparatus to a lifting device. The heater could then be lifted from thebottom chamber of a Czochralski-type crystal puller machine for machinecleaning or heater replacement. These same devices are also used toplace a new heater in the puller machine.

The above device, and similar devices, are appropriate for siliconmanufacturing operations. However, they have a number of parts that mustbe assembled prior to and during the lifting, thereby consuming operatorand machine time. This assembly and disassembly results inmetal-to-metal contact among the device's parts, within the assembly,potentially damaging the device. Additionally, heat transfer from theheater the lifter, resulting from contact between the heater and thelifter, can cause the lifter to warp, leading to the added cost and timeof replacement parts; it also increases the temperature of the lifter,thereby requiring a cooling period before the lifter can be handled.

SUMMARY OF THE INVENTION

In view of the above problems, an object of the present invention is toprovide an apparatus and method for lifting and positioning a device,such as a circumferential heater, with reduced operator “hands-on”activity. The present device can be lowered into the center of acircumferential heater, the sling foot pads positioned under the heater,and the heater and lifter combination lifted by a single operator, usinga remote control box. The present invention improves on past devices dueto an operator's ability to operate it from a distance, reducedmetal-to-metal contact, and ease of use.

The present invention also has relatively few parts. This reduces theamount of time an operator must spend setting up and taking down theapparatus, thereby enabling a more efficient process. Additionally, thepresent invention is, essentially, a one-piece construction afterassembly. This helps to control warpage and commensurate part misfits.

Another improvement over the prior art is the present invention'selimination of an exterior cage. As opposed to prior heater-liftingdevices, which enclosed the heater within a cage or similar means, thepresent invention lifts a circumferential heater from within its centervoid. This interior placement eliminates the need for an exterior cage,thereby reducing operator time, warpage, and heat transfer, as describedabove.

The present invention also reduces metal-to-metal contact by usingpolymer-based, ceramic, graphite, carbon composite or equivalentbushings and pads. These pads protect both the lifter and the heaterfrom damage, and keep the lifter cooler than the previous lifterdevices. The pads have the additional benefit of not contributing metalcontamination to the Czochralski process.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described by reference to the examples and thedrawings, in which:

FIG. 1 is a side view of a preferred embodiment of the presentinvention, with slings extended and support rod in the up position.

FIG. 2 is a top view of a preferred embodiment of the present invention.

FIG. 3 is a side view of the support rod.

FIG. 4 is a top view of the top support.

FIG. 5 is a top view of the bottom support.

FIG. 6 is a front side view of an outer sling.

FIG. 7 is a front side view of a middle sling.

FIG. 8 is a side view of a representative sling.

DETAILED DESCRIPTION OF THE INVENTION

As delineated in the drawings, and shown in FIG. 1, the presentinvention comprises a support rod 10, a top support 20, a bottom support30, and a plurality of slings 40.

As shown in FIG. 3, a support rod 10 comprises a support rod shaft 12, abottom pad 14 removably attached to a distal end of the shaft 12, a toppad 16 removably attached to the end of the shaft 12 opposite the bottompad 14, and a hoist mechanism 18 attached to the surface of the top pad16 opposite the shaft 12.

The top support 20, as shown in FIG. 4, comprises a hoist mechanism 22attached to the top surface of the top support 20, a center void 24running vertically through the center of the top support 20, and aplurality of removably attached pivot shafts 26. In a preferredembodiment, the pivot shafts 26 as shown in FIG. 4 are seated inthree-sided notches 28 spaced about the outer edge of the top support20. The shafts 26 and notches 28 are distributed reasonably equallyabout the circumference of the top support 20, and are sized such that asling 40 fits into a notch 28. The notch 28 is wide and deep enough sothat the sling 40 can swing freely, but narrow enough so that the sling40 has limited horizontal play within the notch 28.

The bottom support 30, shown in FIG. 5, comprises a center void 32 and aplurality of circumferential slots 34. The slots 34 are arrangedsubstantially similar to the upper support pivot shafts 26 and notches28, but are located a greater distance from the bottom support centervoid 32 than the pivot shafts 26 are from the top support center void24.

A representative sling 40 is shown in FIG. 1. The sling 40 has a rigidbody 42 and foot plate 44 as shown in FIG. 8. Fixed stoppers 46 arelocated approximately medially on the rigid body 42 of the slings. Acylindrical void 48 at one end of the rigid body 42 attaches to the topsupport pivot shafts 26. The foot plate 44 attaches to the other end ofthe rigid body 42. In a preferred embodiment of the invention, theslings comprise middle slings 50 (FIG. 7) and outer slings 52 (FIG. 6).In such an embodiment, the middle slings 50 are wider than the outerslings 52. The differing widths are necessary in this embodiment becauseof the configuration of the workpiece supports. If required, all of theslings could be of varying or equal widths, depending on the workpiece.

As shown in FIGS. 1, 4, and 5, the invention is configured such that thesupport rod shaft 12 runs through both the top support center void 24and the bottom support center void 32. The bottom pad 14 is disposedbelow the bottom support 30 such that when the invention is in asubstantially upright position, the bottom support 30 is supported bythe bottom pad 14. The support rod top pad 16 is disposed above the topsupport 20 such that the top support 20 is at all times between the toppad 16 and the bottom support 30.

In a preferred embodiment of the invention, though it would not be solimited, a washer (not shown), composed of a polymer-based,heat-resistant material such as Teflon®, covers the inside surface ofthe top and bottom support center voids 24 and 32 so as to minimizemetal-to-metal contact between the support rod 10 and the top support 20and bottom support 30.

The slings 40 are swingably connected by pivot shafts 26 to the topsupport 20 such that the cylindrical void 48 of the slings 40 fits intothe notches 28 of the top support 20. In a particular embodiment of theinvention, though it would not be so limited, a bushing (not shown),composed of a polymer-based, heat-resistant material such as Teflon®, oranother non-metallic, heat resistant material such as a ceramic, isutilized in combination with the pivot shaft 26 such that minimalmetal-to-metal contact occurs between the sling 40 and the top plate 20.

In a preferred embodiment, a polymer-based, heat-resistant material suchas Teflon® can be used to form pads 45. The pads 45 are fixably attachedto the upper surface of the foot plate 44 of the sling 40. In additionto a polymer-based material, other heat-resistant, non-metallicmaterials, such as ceramic, could be utilized in the bushings, washers,pads, and other heat protective elements included in the invention.

The slings 40 pass through the slots 34 of the bottom support 30. Thebottom support 30 has a range of motion slidably along the slings withupper and lower limits at the medially positioned stoppers 46 and thesling foot plate 44. In a preferred embodiment of the invention, thoughit would not be so limited, the interior of the slots 34 are lined witha polymer-based, heat-resistant material such as Teflon® or equivalent.The heat resistant material would extend outwardly along the upper andlower surface of the bottom support 30 such that when in the openposition there is minimal metal-to-metal contact between the bottomsupport 30 and the sling stoppers 46.

In a preferred method, the apparatus would be used to raise, lower, andposition a circumferential heater into the lower portion of aCzochralski-type puller machine utilized in the semiconductor industry.One skilled in the art, however, could utilize both the apparatus andthe method in any situation where the workpiece has an interior voidsuitable for insertion of a circumferential lifter as disclosed herein.

In a preferred method, beginning with the step where the apparatus isoutside the heater, and the heater is to be lifted out of the pullermachine for cleaning, replacement, or other suitable reason, an operatorattaches a support line or similar device to the top support hoistmechanism 22. The support line could be secured to the hoist mechanismby means of a hook, or quick release securing device or equivalent. Theoperator then raises the apparatus, and lowers the apparatus into thepulling machine such that the apparatus is positioned in the interior ofthe circumferential heater. The operator then repositions the supportline from the top support hoist mechanism 22 to the support rod hoistmechanism 18. The operator then places tension on the support line,thereby causing the support rod 10 to rise. The rising support rodcauses the slings 40 to extend outward and under the circumferentialheater. The heater-lifter combination is then ready for lifting orrepositioning. The operator can then raise the heater-lifter combinationout of the puller machine, and position it on the shop floor or otherdesired location. After the heater-lifter combination is placed at thedesired position, the support line is slacked, causing the support rod10 to lower. The lowering support rod causes the slings 40 to retract,thereby disengaging the heater from the lifter. The lifter can then beextracted from the interior of the heater by repositioning the supportline from the support rod hoist mechanism 18 to the top support hoistmechanism 22, and lifting the lifter.

What is claimed is:
 1. A lifting apparatus comprising: (a) a topsupport, said top support having a top surface and a bottom surface thatlay in a substantially horizontal fashion and a diameter, said topsupport including a void running vertically through the center of saidtop support, said void having sufficient diameter to accommodate asupport rod's shaft, a plurality of removable attached pivot shaftsspaced along the outside circumferential edge of said top support, and ahoist mechanism attached to said the top surface of said top support;(b) a bottom support, said bottom support having a top surface and abottom surface that lay in a substantially horizontal fashion and adiameter greater than said diameter of the top support, said bottomsupport including a void having sufficient diameter to accommodate asupport rod's shaft running vertically through the center of said bottomsupport, and a plurality of slots, said slots located a distance fromthe center of the support that is greater than the distance from thecenter of said top support to said pivot shafts of said top support; (c)a support rod, said rod having a shaft running through the voids of saidtop support and said bottom support, a bottom pad removably attachedperpendicularly to one end of said shaft and located below the bottomsurface of said bottom support, and a top pad removably attachedperpendicularly to the other end of said shaft wherein said top pad hasa hoist mechanism attached to the surface opposite where said shaft isattached and where said top pad is located above the top surface of saidtop support, wherein each pad constrains said top and bottom supports toslide along said support rod; and (d) a plurality of slings, each ofsaid slings having a rigid body running through the slots of said bottomsupport, a cylindrical void at one end of said rigid body that attachesto the pivot shafts of said top support, a foot plate removably attachedon the opposite end of said rigid body and at an oblique angle to saidrigid body such that the foot plate is substantially horizontal, and astopper removably attached to said rigid body between the foot plate andthe cylindrical void and assembled between the bottom surface of saidtop support and the top surface of said bottom support such that thesling can slide through the slots on said bottom support from the footplate of said sling to the stopper on the rigid body of said sling. 2.The lifting apparatus of claim 1 further comprising: (a) heat resistantbushings, said bushings disposed between: (i) said top support and saidplurality of slings at the top support—sling interface; (ii) saidsupport rod shaft and said top support at the interface of said supportrod shaft and said top support center void; (iii) said support rod shaftand said bottom support at the interface of said support rod shaft andsaid bottom support center void; and (iv) said plurality of slings andsaid bottom support slots, at the interface of said plurality of slingsand said bottom support slots.
 3. The lifting apparatus of claim 1further comprising: (a) heat resistant pads positioned on said footplate of said slings, said pads fixably attached to a face of said lowerportion of said sling which substantially faces said bottom support. 4.A method for positioning a workpiece utilizing the apparatus asdescribed in claim 1 comprising: (a) placing a lifting apparatus inposition; (b) imparting an upward force upon said support rod hoistmechanism such that said slings extend outwardly and under saidworkpiece; (c) lifting said apparatus and said workpiece; (d) placingsaid apparatus and said workpiece at a desired location; (e) loweringsaid support rod such that said slings retract inwardly; (f) impartingan upward force upon said top support hoist mechanism; and (g)withdrawing said lifting apparatus from said workpiece.
 5. The method ofclaim 4 wherein the workpiece is a circumferential heater used in themanufacture of silicon ingots.